In Long Term Evolution (LTE for short) systems of releases 8, 9, and 10, each LTE carrier is backward compatible, that is, each LTE system of a later release can support access and data transmission of a user equipment of an earlier LTE release. Each subframe of a backward compatible carrier has a control region. The control region is in first n symbols of a subframe in a time domain and occupies a bandwidth of the whole carrier in a frequency domain, where n is a natural number ranging from 1 to 4. The control region bears downlink control channels such as a physical downlink control channel (PDCCH for short), a physical hybrid automatic repeat request indicator channel (PHICH for short), and a physical control format indicator channel (PCFICH for short). Demodulation of the foregoing downlink control channels is based on a cell-specific reference signal (CRS for short). The CRS is used for data demodulation, time and frequency synchronization and tracking, channel interference, radio resource management measurement, and the like, on a backward compatible carrier. When a base station has no data to be sent in a certain subframe, the base station also sends a CRS in the subframe; therefore, the energy efficiency of the base station is relatively low.
In Long Term Evolution-Advanced (LTE-A for short) systems of release 11 and a release later than release 11, a new carrier type (NCT) is introduced. A new carrier does not support access and data transmission of a user equipment (UE for short) of an earlier LTE release, and supports access and data transmission of a UE of a new release of the LTE system. It is allowed that the NCT does not have a control region on a backward compatible carrier, that is, a PDCCH is not sent, and the PDCCH is replaced by an enhanced physical downlink control channel (ePDCCH for short). Different from the PDCCH, the ePDCCH is transmitted based on channel precoding. A resource configuration of the ePDCCH is similar to that of the PDCCH, that is, assignment is implemented through an RB pair. The ePDCCH is demodulated based on a UE-specific reference signal (UERS for short).
In LTE-A systems of release 11 and a release later than release 11, the NCT does not have a control region. If an ePDCCH cannot be sent on the NCT, it is possible that the NCT cannot be used to schedule a user equipment or implement downlink feedback for uplink data of the user equipment. For example, the ePDCCH cannot be sent in a multimedia broadcast multicast service single frequency network (MBSFN for short) subframe or in special subframes in special subframe configurations 0 and 5 of a time division duplex (TDD for short) system, and uplink or downlink scheduling of the user equipment cannot be implemented. Specifically, if a multicast or broadcast service is transmitted in an MBSFN subframe, all resource block pairs (RB pair) of the current carrier are used for multicast or broadcast, that is, no RB pair is assigned to the ePDCCH; for special subframes in TDD special subframe configurations 0 and 5, a downlink timeslot part has only three symbols, and resources are few, so an ePDCCH cannot be sent.